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Why in Batch/DOS (or whatsoever language),REM does make a difference?

Why in Batch/DOS (or whatsoever language), "To avoid this pitfall force CommandBlock2 to succeed, i.e. using a simple REM as last block command: Command1 && (CommandBlock2 & REM) || (CommandBlock3) " could work? My question is why adding a remark would change the conditional execution?

Solution

  • npocmaka has given the answer already.

    DOS Tips article about Conditional Execution explains:

    Be careful when combining the operators, i.e.:
    Command1 && (CommandBlock2) || (CommandBlock3)

    • If Command1 fails then CommandBlock2 will be skipped and CommandBlock3 will be executed.
    • If Command1 succeeds then CommandBlock2 will be executed.
    • If Command2 fails then CommandBlock3 will also be executed!!

    To avoid this pitfall force CommandBlock2 to succeed, i.e. using a simple REM as last block command:
    Command1 && (CommandBlock2 & REM) || (CommandBlock3)

    or:

    Command1 && (
       CommandBlock2
       REM force success
    ) || (
       CommandBlock3
    )